Actually, BYU is 18th in getting the ball in the hoop, and 35th in Defense. Defense has to get better.
But, yeah, BYU is #21 on Pomeroy, primarily because the win over Oregon has diminished as Ducks have sunk down to #52 since BYU won that game.
Poor 3 point shooting has been more than offset by dominant offensive rebounding and reduced turnover rate.
These two factors raise BYU offensive efficiency to elite level. Offensive rebounds negate a missed shot. Avoiding turnovers increases chances at the rim.
Moreover offense will get ever better when the arc shooting rises to 35%.
Defense has to improve for BYU to be a real top 10 team.